1. Field of the Invention
The present invention relates to an on-vehicle apparatus for receiving service information sent from a road infrastructure to perform cruise assist as a driving support system, and in particular to an information display system and an information display method for displaying received service information.
2. Description of the Related Art
In recent years, as a technology for traffic-safety utilizing an information communication technique, the ITS (Intelligent Transport System) has been developed. As one kind of this ITS, there is the AHS (Advanced Cruise-Assist Highway System). In this AHS, a system on a road side (road infrastructure) and an on-vehicle apparatus on a vehicle side communicate with each other, whereby the road and the vehicle unite to perform cruise assist.
One form of cruise assist is provision of information, and information concerning events (e.g., curves, stopped vehicles, crossings, etc.) existing in a service section on a road is provided to crew members (in particular, a driver) of a vehicle. In the AHS, although contents of the information sent from the road infrastructure to the on-vehicle apparatus are decided as a standard, it is left to the autonomy of a manufacturer how the contents of the information received by the on-vehicle apparatus are provided to the driver. As a method of provision of information to the driver, for example, there is display of information using a display apparatus provided in the vehicle (e.g., see the following Patent Documents 1 and 2). In such a method, it displays a symbol corresponding to an event which the vehicle is about to reach (or characters or the like corresponding to content of such a event) based upon the information received from the road infrastructure, whereby the driver is provided with the information.                [Patent Document 1]                    JP-A-2001-101593                        [Patent Document 2]                    JP-A-2001-101594                        
In such a display apparatus, from the viewpoint of provision of information to a driver, its significance is attained by displaying a symbol corresponding only to a closest event which a vehicle is about to reach. However, from the stand point of the driver who is provided with the information, the information is likely to be insufficient through such a method of display of information. In order to drive comfortably, it is desirable for the driver to generally know what kinds of events exist on a road which the driver's own vehicle is about to reach. This is because, comparing a state in which the driver generally knows events on a road which the driver's own vehicle is about to reach with a state in which the driver knows the events on the road only partially, the former state gives less mental burden to the driver in terms of guaranteeing predictability. In addition, in terms of provision of information as cruise assist, this provision of information has an implication of drawing the driver's attention to an event. Therefore, in the case in which information is provided to the driver, it is also important to perform at least display of information considering calling the driver's attention.